Write a function to optimize a given dataset for faster retrieval.
Interpret optimization as building an inverted index. The input is a list of records, where each record is a dictionary with a unique integer id and string text; ignore other fields. Return a dictionary mapping each lowercase alphanumeric token to a sorted list of record IDs containing that token. Treat repeated tokens within one record as one occurrence, and omit records with no tokens.
Function signature: def optimize_dataset(dataset):
def optimize_dataset(dataset):